Liquid crystal display apparatus and method for checking the joining accuracy thereof

ABSTRACT

The present invention provides an LCD apparatus and a method for checking the joining accuracy thereof The LCD apparatus comprises an LCD panel, a printed circuit board and a package unit coupled to the LCD panel. On the printed circuit board, there is a plurality of first pins, a fir check pad and a second pad, wherein at least one fist pin is electrically connected to the first check pad and at least another first pin is electrically connected to the second check pad. There is a plurality of second pins on the package unit, wherein the second pins join the first pins on the printed circuit board correspondingly to connect the first pins electrically. To check the joining accuracy of the LCD apparatus, electric resistance is obtained by measuring the resistance between the first and second check pad with an ohmmeter. When the measured resistance is below a reference value, the assembly quality of the LCD is not qualified.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional application of a pending application Ser. No.09/993,441, filed Nov. 13, 2001 now U.S. Pat. No. 6,714,275.

FIELD OF THE INVENTION

The present invention relates to a liquid crystal display, and moreparticularly to an improved liquid crystal display apparatus and methodfor checking the joining accuracy thereof

BACKGROUND OF THE INVENTION

Conventionally, a liquid crystal display apparatus comprises a panel, adrive circuit and a control circuit. The pixels on the panel are drivenby the drive circuit and the control circuit is designed to manipulatethe drive circuit to control images displayed on the panel. In a liquidcrystal display apparatus, the drive circuit is generally set on tapecarrier packages (TCP) and the control circuit is laid out on a controlcircuit board. The TCP is coupled to the panel and the control circuitis coupled to the TCP, wherein the pins on the control circuit areconstrained in a predetermined ring to correspond with pins on the TCPto maintain the display quality of the liquid crystal apparatus.Therefore, there is a need to check the joining accuracy of the pins toensure the quality of the LCD. FIG. 1 shows the conventional method forchecking joining accuracy of the pins on the control circuit board andthe LCD panel of an LCD apparatus. TCP 1 is coupled to the controlcircuit 2, and it is difficult to observe the pins 3 on the controlcircuit 2 because TCP 1 blocks them. One way to check the joiningaccuracy of the pins is to cut a detection window 5 along the edge ofTCP 1 to expose one pin 3 on the control circuit 2 for comparison withthe corresponding pin 4 on TCP. All of the pins 3 and 4 are parallel andthe pins 3 on the control circuit are designed to correspond with thepins 4 on TCP. If the exposed pin 3 in the detection window 5 is joinedto the corresponding pin 4 approximately, the rest of pins match aswell.

Conventionally, the pins 3 on the control circuit are joined to the pins4 on TCP with solder. However, anisotropic conductive film (ACF) hasbecome popular for joining the pins. When the anisotropic conductivefilm (ACF) is used to join the pins 3 on the control circuit to the pins4 on TCP, the adhesive resins that are squeezes out will block theobservation through the detection window 5. Therefore, it is not easy tocheck the joining accuracy of the pins when the anisotropic conductivefilm is chosen to join the pins 3 and 4.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystaldisplay apparatus to easily check the joining accuracy of the pins onthe control circuit board and the LCD panel.

Another object of the present invention is to provide a method forchecking the joining accuracy of the pins on the control circuit boardand the LCD panel by measuring the electric resistance between the pinsthereon.

To achieve these advantages, a liquid crystal display (LCD) apparatuscomprises an LCD panel a printed circuit board and a package unitcoupled to the LCD panel. On the printed circuit board, there is aplurality of first pins, a first check pad and a second pad thereon,wherein at least one first pin is electrically connected to the firstcheck pad and at least another first pin is electrically connected tothe second check pad. There is a plurality of is second pins on thepackage unit, wherein the second pins join the first pins on the printedcircuit board correspondingly to connect the first pins electrically.

In another aspect of the present invention provides a method forchecking assembly accuracy of the pins on an LCD apparatus comprisingthe steps of:

providing a first check pad and a second check pad on the printedcircuit board;

connecting at least one first pin to the first check pad;

connecting at least another first pin to the second check pad; and

measuring electric resistance between the first and the second pad todetect the electric resistance between the first and second pins.

According to another aspect of the present invention, the package unitis a tape carrier package (TCP) and the package unit further comprises adriving circuit thereon for driving the LCD panel. The printed circuitboard further comprises a control circuit thereon for controlling thedriving circuit. The first pins on the printed circuit board can bejoined with the second pins on the package unit by anisotropicconductive film ACF or solder.

BRIEF DESCRIPTION OF THE DRAWING

The above objects and other advantages of the present invention willbecome more apparent by describing in detail a preferred embodimentthereof which reference to the attached drawings in which:

FIG. 1 is a schematic drawing illustrating the conventional design forchecking joining accuracy of the pins on the control circuit board andthe LCD panel;

FIG. 2 is a schematic drawing illustrating an LCD apparatus according toone embodiment of the present invention;

FIGS. 3a and 3 b are cross sections of an LCD apparatus according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 shows an LCD apparatus 100 according to one embodiment of thepresent invention. The LCD apparatus 100 comprises an LCD panel 10, aprinted circuit board 20 and a plurality of tape carrier packages(CP)30. There is a plurality of first pins 21, a first is check pad 22, asecond check pad 23, and a control circuit (not shown) on the printedcircuit board 20. On the tape carrier packages (TCP) 30, there aredriving circuits 31 on each for driving the LCD panel 10, and aplurality of second pins 32 for joining the first pins on the printedcircuit board 20 correspondingly. The tape carrier packages are coupledto the LCD panel 10 and the second pins 32 thereon are joined to thefirst pins 21 to assemble the tape carrier packages 30 and the printedcircuit 20. The first pins 21 and the second pins 32 are joined byanisotropic conductive film or solder. The amount of the tape carrierpackages 30 and the second pins 32 thereon depends on the number ofpixels displayed in the LCD panel 10's selected resolution.

On the printed circuit board, at least one first pin 21 is electricallyconnected to the first check pad 22 and at least another first pin 21 iselectrically connected to the second check pad 23. FIG. 3a and 3 b showthe cross sections of the LCD apparatus in FIG. 2 along the A-A′ hatch.In FIG. 3a and 3 b, two adjacent first pins 21 are electricallyconnected to the first check pad 22 and the second check pad 23respectively. The two adjacent first pins 21 are close but stillseparated from each other. Therefore, by measuring the electricalresistance between the first check pad 22 and the second check pad 23with an ohmmeter, an equivalent resistance between the two adjacentfirst pins 21 can be obtained. The value of the measured equivalentresistance is proportional to the distance between the first pin 21 andthe adjacent second pin 32. In FIG. 3a, the first pins 21 on the printedcircuit board 20 are joined with the second pins 32 on the tape carrierpackages 30 precisely with conductive material C, e.g. anisotropicconductive film or solder, and the distance between the first pins 21and the adjacent second pin 32 is D, the maximum distance. In FIG. 3b,the first pins 21 on the printed circuit board 20 are joined with thesecond pins 32 on the tape carrier packages 30 inaccurately, andtherefore the distance between the first pins 21 and the adjacent secondpin 32 is d, less than D. The measured equivalent resistance is FIG. 3bis smaller than at in FIG. 3a because d<D.

There is an impedance circuit formed when the first check pad 22, thesecond check pad 23, the first pins 21 connecting to the check pad 22and 23 and the second pins 32 corresponding to the first pins 21 areconnected. The maximum equivalent resistance is obtained when thedistance between the first pins 21 and the adjacent second pin 32 is D.When the distance d is smaller than D, which means the first pins 21 onthe printed circuit board 20 are joined with the second pins 32 on thetape carrier package 30 inaccurately, the equivalent resistance measuredwill be smaller than the maximum equivalent resistance. A referenceequivalent resistance can be predetermined according to the maximumvalue. After the LCD panel 10 is assembled with the printed circuitboard 20 by the tape carrier packages 30, an equivalent resistance canbe measured by an ohmmeter which connects the first and second check pad22 and 23. If the measured equivalent resistance is below the referencevalue, the joining quality of the pins 21 and 32 of the LCD apparatus isnot qualified.

According to the present invention, even when anisotropic conductivefilm is chosen to join the pins 21 and 32 and excess material blocks thejoined pins 21 and 32, it is still easy to check the joining accuracy ofthe pins by measuring the equivalent resistance.

The foregoing description of the preferred embodiments of this inventionhas been presented for purposes of illustration and description. Obviousmodifications or variations are possible in light of the above teaching.The embodiments were chosen and described to provide the bestillustration of the principles of this invention and its practicalapplication to thereby enable those skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. All such modifications andvariations are within the scope of the present invention as determinedby the appended claims when interpreted in accordance with the breadthto which they are fairly, legally, and equitably entitled.

What is claimed is:
 1. A method for checking joining accuracy of aplurality of first pins on a printed circuit board and a plurality ofsecond pins on a package unit wherein the package unit is coupled to anLCD panel with the second pins thereon corresponding to the first pinsfor electrically connecting printed circuit board and the LCD panel, themethod comprising the steps of: providing a first check pad and a secondcheck pad on the printed circuit board; connecting at least one firstpin to the first check pad; connecting at least another first pin to thesecond check pad; and measuring electric resistance between the firstand the second pad to get the electric resistance which represents theelectric resistance between the first and the second pins.
 2. The methodas claimed in claim 1, wherein the package unit is a tape carrierpackage (TCP).
 3. The method as claimed in claim 2, wherein the packageunit comprises a driving circuit thereon for driving the LCD panel. 4.The method as claimed in claim 3, wherein the printed circuit boardcomprises a control circuit thereon for controlling the driving circuit.5. The method as claimed in claim 4, wherein the second pins areelectrically connected to the first pins by a anisotropic conductivefilm (ACF).
 6. The method as claimed in claim 4, wherein the second pinsare electrically connected to the first pins by solder.